“…These large nanocubes were likely formed through a self-multiplication process. Such a growth mechanism has been described as a “cementing mechanism” or an “oriented attachment” and has been discussed in detail in several reports. − In the current case, this mechanism is strongly supported by observations of diminishing intercube space and of various combination modes of primitive nanocubes (inset, Figure B). The formation and division of these lamellar micelles will be further addressed later.…”
Self-generation of ionic organic capping from nonionic surfactant polyoxyethylene (20) sorbitan trioleate (Tween-85) has been realized for the controlled synthesis of single crystalline Co(3)O(4) quantum dots (3.0-5.7 nm) in cubic morphology from related layered hydroxide precursors at 80-95 degrees C. With chemical modification of hydrophobic functional groups on the surface of Co(3)O(4) nanocubes; furthermore, various nanocube-containing micellar superstructures can be further assembled through hydrophobic interactions between Tween-85 molecules and the surface coating under "one-pot" conditions. In particular, square arrangements, spherical domains, and line-assemblies of the prepared Co(3)O(4) nanocubes and their inter-transformations have been attained for the first time by manipulating intersurfactant-interactions. Hydrolysis of Tween-85 and the resultant tiered surfactant superstructures have been investigated with FTIR/UV-vis/EA/TGA/DTA/XPS methods, and the capping species has been identified to be alkylated oleic carboxylate anions derived from Tween-85. Pronounced quantum confinement effects have been observed with the prepared Co(3)O(4) nanocubes, and the optical band gap energies determined are 3.95 and 2.13 eV, respectively, for O(2-)--> Co(2+) and O(2-)--> Co(3+) charge-transfer processes.
“…These large nanocubes were likely formed through a self-multiplication process. Such a growth mechanism has been described as a “cementing mechanism” or an “oriented attachment” and has been discussed in detail in several reports. − In the current case, this mechanism is strongly supported by observations of diminishing intercube space and of various combination modes of primitive nanocubes (inset, Figure B). The formation and division of these lamellar micelles will be further addressed later.…”
Self-generation of ionic organic capping from nonionic surfactant polyoxyethylene (20) sorbitan trioleate (Tween-85) has been realized for the controlled synthesis of single crystalline Co(3)O(4) quantum dots (3.0-5.7 nm) in cubic morphology from related layered hydroxide precursors at 80-95 degrees C. With chemical modification of hydrophobic functional groups on the surface of Co(3)O(4) nanocubes; furthermore, various nanocube-containing micellar superstructures can be further assembled through hydrophobic interactions between Tween-85 molecules and the surface coating under "one-pot" conditions. In particular, square arrangements, spherical domains, and line-assemblies of the prepared Co(3)O(4) nanocubes and their inter-transformations have been attained for the first time by manipulating intersurfactant-interactions. Hydrolysis of Tween-85 and the resultant tiered surfactant superstructures have been investigated with FTIR/UV-vis/EA/TGA/DTA/XPS methods, and the capping species has been identified to be alkylated oleic carboxylate anions derived from Tween-85. Pronounced quantum confinement effects have been observed with the prepared Co(3)O(4) nanocubes, and the optical band gap energies determined are 3.95 and 2.13 eV, respectively, for O(2-)--> Co(2+) and O(2-)--> Co(3+) charge-transfer processes.
“…This type of interconnection can be achieved through branching (9b) or locking. As reported in Figure c, two butterflies are locked with a small, thin crystallite platelet (marked with an arrow), indicating a cementing mechanism (i.e., combination of primary crystallites) is operative for the butterfly stacking. 9 TEM images of rotation and locking in butterfly-like β-Co(OH) 2 formed in stage II precipitation: (a) a single butterfly at two different focus levels, (b) 60° rotation, and (c) locking between the two butterflies with a small crystallite (indicated by an arrow).…”
A synthesis of beta-Co(OH)2 nanocrystalline materials has been investigated with the assistance of chelating agent ethylenediamine. By controlling precipitation processes, various forms of beta-Co(OH)2 crystallites can be prepared at different stages. The crystallite morphologies include two-dimensional hexagonal sheet platelets, one-dimensional nanorods, and butterfly-like nanocrystallite intermediates. In particular, a triangular construction unit for beta-Co(OH)2 crystallites has been revealed with the ethylenediamine mediation in the synthesis. With the successful arrest of these butterfly-like intermediate crystallites, especially of linearly aligned "butterflies", the formation mechanism of one-dimensional nanorods or nanoribbons has been experimentally explained. The chemical composition of solution precursors and resultant beta-Co(OH)2 crystallites has been analyzed with UV-vis/FTIR/CHN /XRD/TGA/TEM/SAED methods. The relationships among various observed crystallite morphologies have also been discussed on the basis of the experimental findings.
“…The short nanorods are attached to one another using their low Miller-indexed crystal planes, {001}, {100}, and {110} surfaces, respectively. This type of crystallite growth has been well-known in recent years, and can be described to a cementing process or an “oriented attachment” in nanoscale regime in which a larger crystal structure is formed from smaller ones by direct joining of suitable crystal planes. − The examples observed in the recent years include TiO 2 nanocrystallites, β-Co(OH) 2 nanoplatelets, ZnO nanorods, and α-MoO 3 nanoforks. − ,− In the netted structures of Figure (iii and iv), attachment with two {110} crystal planes results in a turning of nanorod alignment and an angle of 107.8° departing two different sets of nanorods in the planar networks (Figure d). The required crystal facets of {110} in this self-attachment are indeed present in the short nanorods [Figure (ii), Figure ] due to the slower growth.…”
Section: Resultsmentioning
confidence: 96%
“…This type of crystallite growth has been wellknown in recent years, and can be described to a cementing process or an "oriented attachment" in nanoscale regime in which a larger crystal structure is formed from smaller ones by direct joining of suitable crystal planes. [44][45][46][47] The examples observed in the recent years include TiO 2 nanocrystallites, β-Co(OH) 2 nanoplatelets, ZnO nanorods, and R-MoO 3 nanoforks. [17][18][19][47][48][49] In the netted structures of Figure 5 (iii and iv), attachment with two {110} crystal planes results in a turning of nanorod alignment and an angle of 107.8°departing two different sets of nanorods in the planar networks (Figure 6d).…”
We report several wet-chemical methods for synthesis of one-dimensional CuO nanostructures in water-ethanol mixed solvents at 77-82 °C and 1 atm. Single-crystalline monodispersed CuO nanorods with a selected breadth in the range of 5-15 nm have been prepared by controlling reagent concentrations. The nanorods are preferentially grown along 〈010〉 directions. A two-step continuous process has also been developed to prepare CuO nanorods and ribbons (length up to 1 µm) with a large aspect ratio under pseudo-steady-state operation. Furthermore, a two-dimensional netted structure has been assembled for the first time from short nanorods formed after prolonged aging; the nanorods are attached each other using their {001}, {100}, and {110} crystal planes. With concentrated NaOH used in synthesis, the nanorods can also be extended along 〈100〉, which gives rise to the formation of CuO nanoplatelets. Various synthetic parameters have also been investigated.
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